题目描述

The game “The Pilots Brothers: following the stripy elephant” has a quest where a player needs to open a refrigerator.

There are $16$ handles on the refrigerator door. Every handle can be in one of two states: open or closed. The refrigerator is open only when all handles are open. The handles are represented as a matrix $4\times4$. You can change the state of a handle in any location $[i, j] (1 \leq i, j \leq 4)$. However, this also changes states of all handles in row $i$ and all handles in column $j$.

The task is to determine the minimum number of handle switching necessary to open the refrigerator.

输入格式

The input contains four lines. Each of the four lines contains four characters describing the initial state of appropriate handles. A symbol “+” means that the handle is in closed state, whereas the symbol “−” means “open”. At least one of the handles is initially closed.

输出格式

The first line of the input contains $N$ – the minimum number of switching. The rest $N$ lines describe switching sequence. Each of the lines contains a row number and a column number of the matrix separated by one or more spaces. If there are several solutions, you may give any one of them.

题目大意

【题目描述】

游戏《飞行员兄弟：追寻条纹大象》中有一个任务，玩家需要打开一个冰箱。

冰箱门上有 $16$ 个手柄。每个手柄可以处于两种状态之一：打开或关闭。只有当所有手柄都打开时，冰箱才会打开。手柄被表示为一个 $4\times4$ 的矩阵。你可以改变任何位置 $[i, j] (1 \leq i, j \leq 4)$ 处手柄的状态。但是，这也会改变第 $i$ 行和第 $j$ 列中所有手柄的状态。

任务是确定打开冰箱所需的最小切换次数。

【输入格式】

输入包含四行。每一行都包含四个字符，描述相应手柄的初始状态。符号 “+” 表示手柄处于关闭状态，而符号 “−” 表示 “打开”状态。至少有一个手柄最初是关闭的。

【输出格式】

输入的第一行包含 $N$ - 最小切换次数。接下来的 $N$ 行描述切换序列。每行包含一个矩阵的行号和列号，用一个或多个空格分隔开。如果存在多个解决方案，则可以提供任何一个解决方案。

翻译来自于：ChatGPT。

-+--
----
----
-+--

6 
1 1 
1 3 
1 4 
4 1 
4 3 
4 4